Systemic lupus erythematosus (SLE) is an autoimmune disease that occurs primarily in women (10:1 compared to men) during their childbearing years. In the United States, the prevalence of SLE ranges from 14.6 to 50.8 cases per 100,000 people. The disease is activated by genetic and environmental factors. However, the strongest risk factor for the development of SLE is female gender. The long-term research goal of this project is to delineate mechanisms that control endocrine-dependent gene regulatory networks in the immune system. The objective of this application is to investigate the role of estrogen and its receptors (ER-a/ER-b) in SLE T cell dysfunction. The central hypothesis is that abnormal ER function underpins the failure of SLE T cells to moderate the response to antigen presentation leading to over expression of genes associated with autoimmune disease. The first research goal is to test the postulate that low levels of ER-a expression in SLE T cells contributes to abnormal T cell regulation. The amount of ER-a will be measured in SLE and normal circulating T cells using quantitative polymerase chain amplification and Western blotting. The second goal is to test the hypothesis that lupus pathogenesis occurs because the regulation of ER-dependent signaling is abnormal in SLE T cells. Changes in signal transduction pathways in SLE and normal T cells in response to estradiol will be assessed by microarray. The estrogen response will be blocked with the estrogen receptor antagonist, ICI 182,780, in order to identify molecular pathways and candidate genes for therapeutic intervention. The third goal is to test the hypothesis that Foxp3 is an estrogen gene target that is inappropriately regulated in SLE T cells. Abnormal control of Foxp3 results in a failure of T regulatory cells to dampen the response to antigen and T cell hyperactivation. Co-localization of estrogen receptors and Foxp3 will be measured in SLE and normal T cells using flow cytometry. The effects of estradiol on the ability of SLE regulatory T cells to inhibit proliferation of autologous responder cells will be tested using suppressor assays. The experimental methods include genetic (gene regulation, gene profiling), biochemical (Western blotting, flow cytometry) and cell/molecular (PCR, suppressor assays) approaches. Completion of the proposed research is expected to help identify molecular defects in T cell tolerance that are influenced by estradiol and contribute to the onset and/or progression of SLE. The results will provide the knowledge to carry basic research results towards clinical application and new therapeutic treatments for gender biased autoimmune diseases. PUBLIC HEALTH RELEVANCE: Autoimmune diseases occur when the immune system fails to appropriately regulate itself. Antagonism of the estrogen receptor in women with systemic lupus erythematosus (SLE) results in a significant improvement in disease activity that is accompanied by a reduction in the amount of prednisone administration. The goal of the research proposed in this application is to clarify the basic hormonal-immune dysregulation in SLE so that novel opportunities for specific therapeutic approaches to treat the disease can be developed and improve the quality of patient's lives.